1. Field of the Invention
This invention relates to readers for bar codes which are characterized by a plurality of bars having discrete variations for encoding information therein, and more particularly, to readers which characteristically scan such codes at a non-uniform rate.
2. Prior Art
Bar codes and their associated readers are widely used to facilitate manufacturing, shipment, inventory control of diverse products, such as consumer goods, particularly where large volumes of merchandise are handled. As labor content increases for relatively low priced items, minimization of per piece handling is an economic necessity. The use of bar codes has also arisen from the need for improved efficiencies in light of increased informational content which must be imprinted on the products. This problem is acutely evident in the retailing of foodstuffs where such information as price, date of manufacture, origin and the like is necessitated by law and/or competition.
Numerous schemes of reading bar codes have been proffered, but most have had major shortcomings. A major problem area is in the actual scanning of the bar code. Most systems "read" the information encoded within the series of bars which constitute the code, by detecting the width of successive bars and classifying them according to that system's particular decoding scheme. To obtain an accurate reading, a sensor must traverse the code at a predictable or uniform rate. Accordingly, to reduce undersirable scan-rate variations, complex mechanisms have been developed to pass a sensor by a product bearing a code at a uniform rate. These mechanisms are typically extremely costly and impractical for many applications.
Simple systems have been devised which employ hand held sensors. Being hand held or guided, such readers virtually inherently will scan at a non-uniform rate and thus introduce inaccuracies despite a concerted attempt by the operator not to do so. When passing a hand (and sensor) over a code, there is a human tendency to accelerate or de-accelerate even when making a concious attempt to maintain a constant velocity.
It would be desirable to devise a sensor and decoder which is intended for hand held operation which would compensate for the seemingly inherent inability of humans to move their hands linerally at a uniform rate. A principal object of the present invention is such a decoder system which will accurately detect conventional bar codes at non-uniform read rates.